COMPARISON BETWEEN FREQUENCY-DOMAIN HELICOPTER ELECTROMAGNETIC DATA INVERSION RESULTS BASED ON NUMERICAL SOLUTION OF FAST HANKEL COEFFICIENTS AND LAPLACE’S METHODS

9th International Multidisciplinary Scientific GeoConference - SGEM2009, www.sgem.org, SGEM2009 Conference Proceedings/ ISBN 10: 954-91818-1-2, June 14-19, 2009, Vol. 1, 657-662 pp

ABSTRACT

Nowadays, airborne electromagnetic methods are widely used to investigate subsurface
areas. One of these methods is helicopter electromagnetic method. The basis of inverse
modeling of frequency-domain HEM data is to solve Mundry’s integral numerically.
Various methods have been invented for numerical solution of this integral, such as
Laplace transform, fast Hankel coefficients and Jacobian methods. To analyze
helicopter electromagnetic data, we need inverse programs which can assist us to
achieve the best or accurate interpretation results. Considering that forward modeling
program results can improve or degrade the accuracy of an inversion program, thus, we
need to concentrate of the preliminary model results. The purpose of this paper is to
present and compare the algorithms based on numerical solution of fast Hankel
coefficients and analytical Laplace’s methods, and then investigation of the advantages
and disadvantages of each method. For this, the results obtained from these algorithms
have been investigated using inverse modeling codes. In this regard, we have found that
forward modeling program using Laplace’s method is much faster than Hankel
numerical solution method though writing a code based on Laplace method for this
purpose is more difficult than the Hankel method. Also, by accurate selection of
relevant parameters for the media, we can see that the final results quite approach to
initial model parameters.

Keywords: Helicopter electromagnetic method, Numerical solution of fast Hankel coefficients, Laplace’s method